The home secretary told MPs ultimate blame lay with people smugglers bringing migrants across the channel in small boats.
Home Secretary Suella Braverman was warned four times in September and October her department was potentially breaking the law by keeping migrants at Kent’s Manston centre, MPs have heard.
Previous reports suggested Ms Braverman was told failing to provide alternative accommodation was in breach of the law.
Ms Braverman told the Home Affairs Select Committee she would not comment on leaked documents.
However, she said she was aware from September Manston had a problem.
Manston was designed as a holding site for a maximum of 1,600 migrants who arrive on small boats – each for a maximum of 24 hours – but at its peak there were 4,000 people there.
In October, inspectors found families who had been sleeping on mats in the marquees for weeks.
On Tuesday, the Home Office confirmed the site had been cleared, helped by bad weather in the English Channel causing a sustained fall in the number of crossings.
Dame Diana Johnson, who chairs the Home Affairs Select Committee, said Ms Braverman was told on 15 and 22 September, and 1 and 4 October, that the Home Office did not have the power to detain migrants waiting for onward accommodation.
‘Failed’ border control
Answering a question about asylum seekers in hotels, she said: “We have failed to control our borders, yes, and that’s why the prime minister and myself are absolutely determined to fix this problem.”
The committee heard that 36 people who had been held in Manston had been returned to Albania, under the government’s agreement to return migrants and offenders,
Dan O’Mahoney, the Home Office’s clandestine channel threat commander, also said there was one Albanian police officer working with officials at the Kent camp.
The home secretary is aiming to quadruple the rate at which asylum cases are processed by staff as the government attempts to tackle the backlog in the system.
Ms Braverman told the committee that, on average, each staff member was deciding one asylum case per week at present.
The Home Office has doubled the number of asylum staff to more than 1,000 and plans to recruit another 500 decision-makers by March.
Ms Braverman said: “We want to deliver sustainable changes to reach a minimum of three decisions, per decision maker, per week by May.”
The ambition is four decisions per week, she added.
Rwanda policy
Ms Braverman was also pushed by MPs on the government’s policy to send some asylum seekers to Rwanda in a bid to reduce the numbers crossing the Channel.
The plan, under which the UK has paid Rwanda £140m, is currently on hold as it faces a legal challenge in the court.
The home secretary insisted she still had confidence in the scheme and believed the courts would rule it to be legal.
Matthew Rycroft, the most senior civil servant in the Home Office, said it did not yet have evidence the scheme would be value for money.